With respect to breast cancer detection, the use of palpation by self-exams is still the first line of investigation in diagnosis. There is a long-standing precedent in the medical community to use tissue stiffness as a direct indicator of organ health. In the event of an abnormality detected by palpation or mammographic screening, often traditional imaging modalities such as magnetic resonance (MR), computed tomography (CT) and ultrasonic (US) imaging are employed to enhance and aid medical diagnosis by allowing the non-invasive visualization of internal structure within the breast. Additionally, these modalities are often used to aid in biopsy of suspicious tissue. These more sophisticated imaging modalities have become a standard component of today's clinical armamentarium but have not shown clinical significance with respect to detection and differentiation of cancerous tissue in the breast. Historically, increased mechanical stiffness during tissue palpation exams has been associated with assessing organ health as well as in detecting the growth of a potentially life-threatening cell mass.
In recent years, this need has manifested itself in the creation of less traditional imaging techniques which aim to analyze electrical, optical and mechanical properties of tissue with the goal of finding better diagnostic indicators. For example, electrical impedance tomography is a technique that systematically injects electrical current into the breast and measures the potential at the tissue surface. This data can then be used to reconstruct images of electrical conductivity and permittivity which may be better pathologic indicators. Other examples are near infrared tomography, microwave tomography and elastography. These emerging methods of characterizing tissue have yet to be realized and questions regarding resolution, diagnostic value, and overall capability have yet to be fully reported. When considering past work in ultrasound elastography (USE) and magnetic resonance elastography (MRE), the basis for image reconstruction has been the measurement of displacement or force within or at the boundaries of the tissue of interest.
Elasticity image reconstruction has two immediate uses in the larger medical community. First, it is widely accepted that disease correlates with changes in tissue stiffness, hence the use of palpation techniques for the assessment of tissue health. In addition, recent reports have suggested that diagnostic discrimination of tissue malignancy may be possible using tissue stiffness as a metric. A second application of elastography is concerned with generating accurate computational models for image-guidance applications. The fidelity of these applications will rely heavily on the degree to which the model matches the actual physical description of the organ/tissue of interest. Elastography serves the function of providing patient-specific material properties especially in the region of the pathology, i.e., tumor identification. As such, elastographic imaging techniques (i.e., direct imaging of tissue stiffness) have recently become of great interest to scientists.